The present invention relates to a method and apparatus for drying bearings, especially those conveyed on a production line after being rinsed with an aqueous solvent such as a water. Further, the present invention also relates generally to a vacuum degreasing-drying methods and more particularly to a vacuum degreasing-drying method for degreasing and drying extremely small, precision metal products, especially extra-small diameter miniature bearings and their parts after they have been rinsed with a hydrocarbon cleaning agent.
A method of the sort that has heretofore been employed for drying metal bearings, especially those complicated in configuration, after being rinsed with an aqueous solvent such as water normally comprises the steps of removing moisture sticking to the surface of the bearing, and drying it by the use of organic solvents such as Freon gas and 1, 1, 1-trichloroethane.
Methods other than what has been mentioned above include drying the bearing rinsed with an aqueous solvent such as water by blowing compressed dry air or hot air thereat; by passing it through warm water; by irradiating it with an infrared ray so as to raise the temperature of its surface; by mechanically wiping off moisture sticking thereto; by placing it in a dehydrator to blow moisture off by means of the centrifugal force; and so forth.
Since such a bearing is coated with grease when it is used, it has to be sufficiently dried until the moisture is completely evaporated, irrespective of the drying method for use.
The use of highly volatile freon gas, 1, 1, 1-trichloroethane and the like as in the prior art ensures that a bearing is dried quickly.
Nonetheless, the growing tendency is for the use of freon gas, 1, 1, 1-trichloroethane and the like to be increasingly restricted worldwide in order to protect the ozone layer. For this reason, it has been called for to refrain from using organic solvents such as freon gas, 1, 1, 1-trichloroethane and the like for drying the bearings rinsed with an aqueous solvent such as water as before. Consequently, the use of the aforementioned organic solvents will certainly be prohibited sooner or later as the necessity of the times is emphasized.
If, however, any one of the aforementioned methods is employed for drying the bearings rinsed with an aqueous solvent such as water without using organic solvents such as freon gas, 1, 1, 1-trichloroethane and the like, and if, for instance, the method of blowing compressed dry air at the bearing is adopted, there will develop a hidden portion, depending on the configuration of the bearing. The water stored in this portion tends to increase the time to dry the bearing, thus decreasing bearing manufacturing productivity, rendering difficult the continuous production of bearings and so on. If, otherwise, the method of blowing hot air at the bearing rinsed with an aqueous solvent such as a water or irradiating it with an infrared ray is used, the resulting heat may badly affect a plastic portion such as a retainer or the bearing itself, or may cause the bearing to gather rust, though the drying period is shortened.
In addition, the method of mechanically wiping off moisture sticking to such a bearing by means of, for instance, a dehydrator still poses a problem in that no effect is actually accomplishable effectively.
Further, as conventional methods for degreasing and drying extremely small, precision metal products and the like complicated in configuration after they have been rinsed with a hydrocarbon cleaning agent, those generally used employ, for instance, chlorine organic solvents such as freon and 1, 1, 1-trichloroethane which are highly volatile at the normal temperature, alcoholic organic solvents such as ethanol, highly volatile petroleum hydrocarbon such as gasoline and petroleum benzine, and chemical compound organic solvents such as benzine, hexane and toluene after a hydrocarbon rinsing process. Such organic solvents are employed for degreasing and drying to ensure that even extremely small, precision metal products can be degreased and dried quickly. Particularly, the use of freon and 1, 1, 1-trichloroethane is effective in degreasing and drying extra-small diameter miniature bearings.
Notwithstanding the above, the use of such freon, 1, 1, 1-trichloroethane and the like has been restricted because they cause great destruction of the ozone layer. Moreover, low inflammable organic solvents need to satisfy complete explosion-proof specifications as they are under rigid restrictions due to the fire laws and the use of them costs a great deal. As a result, a number of problems arise when organic solvents are used because the poisoning preventive regulations are applied to the organic solvents, for instance.
Therefore, efforts may be attempted to degrease and dry extremely small, precision metal products without using the aforementioned organic solvents; however, the problems is that it is still impractical to do so because a great deal of time is consumed for drying and because productivity is considerably reduced. When some of the hydrocarbon cleaning agent is left on the surface of such an extra-small diameter, miniature bearing and its parts as it has been dried incompletely, for instance, the application of grease thereto at the following process step may result in lowering the viscosity of the grease, thus causing grease leakage and the spread of the hydrocarbon cleaning agent. In addition to these problems, the acoustic quality of the bearing may deteriorate or the bearing may fail to come in contact with the shaft of a HDD spindle (hard disk drive spindle) motor or the housing, which may cause dust to gather therein.